Accept global title attribute

[awagner-mainz]

Today I wanted to migrate a couple of elements defined in my odd from an inline to a link behaviour. In both cases, I want them to offer some additional information (a normalized tag for the text span being contained in the element) in a hover popup. While in the inline behaviour I have defined a code template <span title="[[title]]">[[content]]</span> and a corresponding title parameter, this did not work so well with the link behaviour. Coming to think of it, title is a global html attribute and I would suggest to offer title as an optional parameter for all behaviours that create "simple" html elements, like (at least) anchor, block, heading, inline, listItem etc.

Whether to implement this in fact as html title attribute or, e.g. for accessibility reasons, in other ways could be a matter of further debate perhaps?